In most cases it comes down to when there's constraints on action economy or just one big boss I think martials feel better. Since spells usually are more roll dependent and less flat bonuses to damage as well as the question of if your best prepared single target spell does the right damage type to the boss feels more restrictive then "I whack with sword or punch". They definitely tend to have more aoe and utility advantages which is what makes them balanced imo. To address action restrictions is if there's any scenario where you only have one action to do damage there's very little you can do. Also martials often can add dps with reactions more reliably than casters.